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The management of protected territories in Bulgaria is a subject to the Bulgarian and European environmental legislation. The used plans for management provide basic information on the condition of abiotic and biotic components of the natural environment in the protected territories and Guidelines for their management, control and conservation. The water resources with their specificity and dynamics of alteration are a major abiotic component that impacts on functioning, development and conservation of ecosystems in these territories. According to the Bulgarian legislation, the surface water resource is determined on the basis of information from the hydrometer stations of the monitoring system in the country maintained by National Institute of Meteorology and Hydrology. The stations of the monitoring network record the actual and available water flows. The major problem of the present investigation is the absence of a monitoring network in the frame of the whole National Park and necessity of realistic water resources determination. National Park Rila is situated in one of the highest mountain catchment areas on the territory of the country with significant water sources. There begin the biggest and the longest Bulgarian rivers as Iskar and Maritza. Despite the status of protected area in the Rila National Park there are no functioning hydrometric stations providing up-to-date information required for the assessment of water resources. [ABSTRACT FROM AUTHOR]

Determination of the maximal run off in the constantly changing urbanized territory often is very different compare to the natural conditions. There are many approaches to reflect the new conditions of flows formation including the extremes. Sometimes the level of urbanization is so quick that the conditions of flows formation could be altered in the frame of several years. The determination of the maximum flows is additionally complicated in case there is not a suitable hydrological monitoring network or a lack of any observations. The last years the rapid growth of the capital Sofia, the biggest city in the Bulgarian Danube catchment area, urgently imposes the new methodological issues for characteristic maximum flows determination necessary for new infrastructural constructions and floods protection activities. Floods are a potential danger for any urban territory where there are river streams. All rivers inflowing trough Sofia urbanized territory spring in the northern slopes of Vitosha Mountain and have a similar hydrological regime. But hydrological observations exist only in one hydrometric station located at the beginning of the city with still low level of urbanization. On the other hand some of the Sofia rivers are heavily impact on the urbanization. The present material considers the determination of maximum characteristic flows of Sofia rivers reflecting the new hydrological conditions in the urban areas. The suitable methodological approaches are discussed and examples with different urbanizations levels on the territory are demonstrated. Landuse mapping is used to identify the existing and expected future land uses. The timely information about the changing pattern of urban land use plays significant role in urban landuse planning and sustainable urban development. The article presents the re-assessment of the maximum natural flows based on the natural flow in the unique monitoring station and generalizing of new hydrological time series depending on the urbanized level. [ABSTRACT FROM AUTHOR]